This invention relates generally to detecting cardiac events, and more particularly, to detecting the closure of the aortic valve.
To evaluate events in specific parts of the cardiac cycle, information about the transitions between the phases is important. Aortic valve closure (AVC) is an important event in the time cycle of the left ventricle, marking the transition from end of ejection to start of diastole. Several methods for determining the timing of AVC exist. Echocardiographic methods include parasternal M-mode of the aortic valve and pulsed/continuous Doppler of the blood flow through the aortic valve. Other methods include phonocardiography of the second heart sound and empirical regression formulas based on heart rate.
Echocardiographic recordings from the apical position provide most tissue Doppler information used in analysis, while the echocardiographic methods for determining the timing of AVC usually use other views or recording modalities, hence giving timing information in separate heart cycles. The heart rate varies from cycle to cycle, and with this heart rate variability the relation between systole and diastole changes, thus changing the timing of the AVC relative to the heart cycle.
Therefore, a need exists for method and apparatus for determining AVC directly, using apical views from the same heart cycle as used in analysis. Certain embodiments of the present invention are intended to meet these needs and other objectives that will become apparent from the description and drawings set forth below.